It is not easy to keep track of evidence in a crime scene investigation. It is necessary for each piece of evidence to maintain a “chain of custody” so that the authenticity of a piece of evidence at trial can be known. At many crime scenes it is also necessary to maintain a log of the personnel entering and leaving the crime scene. The procedures required to maintain the chain of custody and the crime scene log are detail-oriented and if errors are made it can be a big problem later.
It has been proposed to use RFID tags, for example, to try to keep track of evidence and to assist in logging entry and exit of personnel from areas. Most RFID tag designs are not very workable for these purposes, as they are little more than high-tech bar codes that can only be read by a reader such as a handheld “gun” that is placed into close physical proximity with a tag to read the tag. At most crime scenes it is unworkable to try to use close-proximity readers, whether bar-code or RFID. One cannot, for example, count on a person who is entering or exiting a crime scene to do so at a location where such a close-proximity reader is located. Through inadvertence or otherwise, an evidence bag might enter or exit a crime scene boundary at any point along the boundary.
It would be very desirable if a system and method could be devised that would facilitate RF tracking of salient events at a crime scene, that would detect entry and exit at all points along a boundary, and that would more or less continually keep track of who is in the crime scene.